1. Field of the Invention
The present invention is generally related to the treatment of zirconium alloys and, more particularly to treatment to improve surface corrosion performance of zirconium-based material.
2. General Background
Zirconium alloys are widely used in the nuclear industry as cladding and structural materials. Zirconium is a widely accepted material because it has a low neutron absorption cross-section, suitable mechanical properties for intended uses, and a relatively good corrosion resistance. However, the severe environments in which zirconium has been used has led to a variety of approaches to improve its corrosion resistance. Patents of which applicants are aware include the following.
U.S. Pat. No. 4,294,631 discloses a method for improving the corrosion resistance of a body of zirconium alloy to high pressure and high temperature steam. A scanning laser beam heats a surface region substantially equally, without melting, to a temperature range to form a barrier layer of corrosion resistant beta-quenched zirconium alloy at the treated surface.
U.S. Pat. No. 4,718,949 discloses a method of producing a cladding tube for reactor fuel. A zirconium alloy is hot extruded to form a tube and cold rolled and annealed. The annealing is done by heating the inner surface of the tube to a higher temperature than the recrystallization temperature of the zirconium alloy while cooling the outer surface of the tube.
U.S. Pat. No. 4,648,912 discloses a method for improving the high temperature steam corrosion resistance of an alpha zirconium alloy body. The method uses a high energy beam thermal treatment to provide a layer of beta treated microstructure on an alpha zirconium alloy intermediate product. The treated product is then alpha worked to final size.
U.S. Pat. No. 4,279,667 discloses a zirconium alloy having enhanced corrosion resistance to a high pressure and high temperature steam environment by providing an integral surface region of beta-quenched zirconium formed by laser beam scanning.
U.S. Pat. No. 4,576,654; 4,584,030; 4,636,267; 4,664,727; 4,671,826; 4,690,716; 4,717,428; 4,770,847; and 4,879,093 disclose a Variety of methods that involve heat treatment of zirconium based materials.
The known art is directed mainly to annealing by heating or the formation of beta crystals for improved corrosion resistance in boiling or pressurized water reactors and high pressure steam environments. This leaves a need for zirconium-based materials having an improved corrosion resistance in acid environments.